Docker Interview Questions 2026

Have you worked with CI/CD pipelines, and how were they used in your project? Describe the tools used (Jenkins, GitHub Actions, GitLab CI), the stages in your pipeline, how tests were triggered, and how deployments were automated.

Describe the complete CI/CD pipeline you have implemented in your projects. Walk through every stage from code commit to production deployment, including linting, unit tests, build, artifact storage, staging deploy, integration tests, and release gates.

What is the difference between ENTRYPOINT and CMD in Docker? Explain with examples how they interact when both are specified, and how CMD can be overridden at runtime while ENTRYPOINT cannot easily be replaced.

What stages do you generally include in a Jenkins pipeline to ensure code quality? Walk through each stage: checkout, static analysis (SonarQube/ESLint), unit tests with coverage thresholds, security scanning, build, and artifact publishing.

If a critical issue is found in production, what steps would you take to resolve it quickly? Walk through: immediate triage, deciding between hotfix vs rollback, creating a hotfix branch, fast-track CI pipeline, communication protocol, and post-mortem.

Explain your deployment workflow starting from code commit until production release. Cover feature branch → PR → CI → merge → staging deploy → smoke tests → canary/blue-green production deploy → monitoring and rollback plan.

What are the key steps involved in building a Docker image? Explain each Dockerfile instruction (FROM, RUN, COPY, WORKDIR, EXPOSE, CMD), multi-stage builds for smaller images, layer caching best practices, and how to scan images for vulnerabilities.

How do you pass environment variables during Docker build and runtime? Compare ARG (build-time) vs ENV (runtime), how to use --build-arg and --env-file, the security implications of baking secrets into layers, and safer alternatives like Docker secrets.

GKE vs Cloud Run — when would you choose each?